Defrosting and head pressure releasing refrigerating apparatus



Dec. 6, 1960 F. P. CROTSER 2,962,871

DEFROSTING AND HEAD PRESSURE RELEASING REFRIGERATING APPARATUS 2 Sheets-Sheet 1 Filed Dec. 9, 1957 m 5 T NT W0 WDH C 8 M 3 P. K m DH ATTORNEYS Dec. 6, 1960 F. P. cRoTsER 2,962,871

DEFROSTING AND HEAD PRESSURE RELEASING REFRIGERATING APPARATUS Filed Dec. 9, 1957 I I 2 Sheets-Sheet 2 MOTOR COMPRESSOR CONDENSER EVAPORATOR INVENTOR.

A FRANK F? CROTSER ATTORNEYS United Patent DEFROSTING AND HEAD PRESSURE RELEASING REFRIGERATING APPARATUS Frank P. Crotser, Adrian, Mich, assignor to Revco, Inc Deerfield, Mich, a corporation of Michigan Filed Dec. 9, 1957, Ser. No. 701,373

5 Claims. (Cl. 62-155) This invention relates to refrigerating systems, and particularly to refrigerating systems of the type having a compressor that is operated by a compressor motor, the compressor being a pump which compresses a fluid refrigerant in the gaseous phase into a condenser where it is cooled under pressure and thus transformed into the liquid phase, the refrigerant then being emitted from the condenser through a restricted passage into an evaporator where it is retransformed into the gaseous phase, the refrigerant being recompressed, reliquefied and reevaporated through repeated cycles. As the fluid refrigerant is compressed into the condenser its temperature rises and heat is radiated from the condenser. As the refrigerant evaporates in the evaporator under reduced pressure, its temperature falls and heat is absorbed. The evaporator may be located inside of a thermally insulated box which also is arranged to contain food and beverages to be chilled, and sometimes water to be frozen.

A refrigerating system of this type commonly includes a thermostatic circuit controller which, when subjected to temperatures above a predetermined point, causes the compressor motor to be energized, and when subjected to temperatures below a predetermined point causes the compressor motor to be deenergized. The temperature in the environment of the heat sensitive element of the controller, which usually is inside the thermally insulated box, is affected by heat which passes through the Walls of the box at rates which vary with the temperature of the room air and with the heat conductivity of walls and other structures that are in contact with both cool air in the box and warm air in the room. The temperature within the box is affected also by warm air which enters when the box is opened.

Ideally the air inside the box should be maintained at a constant optimum temperature. In practice, however, refrigerating systems of the type to which this invention relates, alternately cool the air in the box to a predetermined low temperature point and then permit the temperature of the air in the box to rise to a predetermined higher point, the low point being below the optimum temperature and the higher point being above the optimum temperature.

When the compressor motor of a refrigerating system of ,the type to which this invention relates is stopped by. the response of a thermostatic circuit controller to a drop in temperature at the heat sensitive element, the head pressure, i.e., the pressure against which the compressor has been working, is lowered gradually as the refrigerant is emitted from the condenser through the restricted passage into the evaporator. The head pressure at the high pressure side of the compressor before the compressor stops may range upwardly from 150 p.s.i. to 200 p.s.i. or more, while the pressure on the low pressure side may range downwardly from 20 p.s.i. to 8 p.s.i. or less. During the time required for the large pressure differential to be reduced sufficiently to permit a motor of practicable size to start without overloading, the temperature within a household refrigerator or freezer rises substantially, particularly when the room in which the box is installed is warm. If the efficiency of the refrigerating system is poor, the time during which the air within the box remains at temperatures that are too high for safe food preservation sometimes is excess1ve.

A compressor motor energizing circuit usually includes a circuit breaking and making mechanism which breaks the circuit when an overload is encountered and remakes the circuit promptly thereafter. A housewife hearing the on and off clicking of such a safety device is likely to become alarmed and to call a serviceman to correct the seemingly faulty refrigerating system.

While a refrigerating system of the type towhich this invention relates might theoretically be equipped with a huge compressor motor which could start against a head pressure of 200 p.s.i. or more, the system would be cumbersome and uneconomical in first cost and in operation. The state of the household refrigeration art is so advanced that what once were regarded as minor deficiencies in economy, in efficacy of operation, in consistency of temperature maintenance, in silence and in foolproofness now may make the difference between competitive commercial success and competitive commercial failure.

Because moisture condenses from air within refrigerator or freezer boxes and congeals upon cool parts of the refrigerating apparatus where it retards absorption of heat, it is necessary to remove or reduce deposits of ice from time to time to prevent the heat absorption properties of the apparatus from being greatly impaired.

Ice that has accumulated on an evaporator can be melted by applying hot gas to the evaporator. The manner in which hot gas is applied to the evaporator is of the utmost importance. Either an excess or a deficiency of defrosting heat is deleterious. Heat applied to any part of the evaporator even slightly in excess of that required to melt off ice is worse than wasted. When heat is employed in excess of that required to melt oft ice, an evaporator quickly turns into a heat radiator.

In some prior art refrigerators the temperature sensitive element of the thermostat has been so conditioned and located as to detect variations in temperature of the evaporator coil. It is most desirable however that the thermostat respond to a composite of variations in the temperature of all parts of the interior of the box. One feature of this invention is the provision of an exhaust which withdraws the interior air rapidly through a port preferably near the floor of the box and returns the air preferably through a slot along the edge of the ceiling of the box. The temperature sensitive element of the thermostat is placed at the port of withdrawal of the thermally homogenized air.

Air inside of refrigerators has been circulated heretofore but this combination of thermostat bulb, exhaust port and return slot or ports is not taught in any prior art known to this inventor.

It is an object of this invention to provide a refrigerating system of the class described in which the differential between the lower temperature at which a compressor pump stops and the higher temperature at which the compressor pump restarts is small, so that the temperature of the air that is being refrigerated is kept nearly uniform.

Another object of the invention is to provide a refrigerating system in which the average interval of time between the stopping and restarting of the compressor pump is short.

Another object of the invention is to provide a refrigerator in which the stopping and starting of the compressor result from a composite of variations in temperatures in all parts of the interior of the refrigerator box. ..=.l'..

.per se is of my invention.

Another object of the invention is to provide a refrigerating system of the class described having means operative during the interval between the stopping and starting of the compressor pump to reduce the head pressure against which the compressor pump must start, and operative at other times to maintain optimum pressure conditions throughout the system. I

A further object is to provide mechanism capable of utilization either for reducing the head pressure against which a compressor motor must start or for applying heat to defrost part of the refrigerating or freezing apparatus.

A further object is to provide a refrigerating system in which the effects of changes in the temperature and humidity of ambient room air and the effects of opening the box door, and of loading commodities into and removing commodities from the box, are minimized.

Another object is to provide a refrigerating system having a single simple valve that performs multiple functions which heretofore have required elaborate valving that was liable to leakage of odoriferous fluid.

And still another object is to provide a refrigerating system having the above mentioned advantages which is low in cost and low in current consumption as well as inexpensive to keep in good order.

Other objects and numerous advantages of the invention will be apparent upon perusal of the following specification as illustrated by the accompanying drawings.

In the drawings:

Fig. I is a view of a refrigerator box constructed in accordance with this invention, the front door and shelving being removed and the top, bottom and side walls being shown in section as indicated by the line I-I of Fig. II;

Fig. II is a sectional view showing the top, bottom and rear walls and a partition plate of the refrigerator box illustrated in Fig. I, an evaporator being shown behind the partition plate, the section being taken as indicated by the line 11-11 of Fig. I;

Fig. III is a diagram showing a preferred form of refrigerating system embodying the instant invention; and

Fig. IV is a fragmentary diagram showing a modification of the system diagrammed in Fig. I.

Neither the compressor motor 1 per se nor the compressor 2 per se nor the condenser 3 per se nor the evaporator 4 per se is of my invention, and neither the manner in which the compressor is connected, by a hot gas conduit 5, to the condenser nor the manner in which the condenser is connected, by a restricted passage 6, to the evaporator nor the manner in which the evaporator is connected by a return conduit 7, to the compressor Therefore, these units and connections are shown schematically.

The system having been charged with fluid refrigerant, the compressor 2 when driven by the motor 1 pumps fluid through the hot gas conduit 5 into the condenser. Heat generated in the fluid by the work done by the compressor is dissipated by radiation from the condenser 3, and as the compressed fluid is cooled it is transformed from the gaseous phase into the liquid phase. From the condenser 3 the fluid is emitted through the restricted passage 6 into the evaporator 4.

Within the evaporator 4 the refrigerant fluid is retransformed from the liquid phase into the gaseous phase, absorbing heat of vaporization and thus chilling the evaporator and the surrounding air. While the compressor is running it maintains a low pressure in the interior of the evaporator by pumping fluid from the evaporator through the return conduit 7.

In order to pre-cool the fluid that passes from the condenser 3 through the restricted passage 6 to the evaporator 4, e.g., at a point where the passage 6 enters an insulated box, the passage 6 is laid in heat exchange relationship with the return conduit 7. This arrangement also warms the return conduit 7 to prevent condensation of moisture thereon. The compressor 2 permits movement of fluid therethrough in one direction only, from the return conduit 7 to the hot gas conduit 5.

A conventional thermostatic control device 8, which is shown diagrammatically for simplicity of illustration, but which may be actuated by a bulb type of thermostat or any other preferred type, is used to maintain an electrical circuit alternatively through a connection 9 or a connection 11. When the temperature to which the thermostatic control device 8 is subjected rises to a predetermined point, the thermostatic control device completes a circuit through the connections 9 and a lead 16 to the motor 1. Completion of the circuit through the connections 9 and the motor 1 causes the motor to start, and the system as above described operates until the temperature falls to a predetermined lower point at which the thermostatic control device is calibrated to open the circuit through the connection 9 and close the circuit through the connection 11. Opening of the circuit through the connection 9 deenergizes the motor 1, and closing of the circuit through the connection 11 activates an electric means such as a solenoid 12 which causes a valve 13 to open a by-pass 14 from the hot gas conduit 5 into the evaporator 4.

The cooperative relationship in which the valve 13 is held open so long as the compressor 2 is not running is an important feature of this invention. It is this relationship that so conditions the pressure within the system that the motor can start against little or no head. Closing of the valve 13 simultaneously with starting of the compressor 2 inaugurates the chilling instantly. As the head pressure builds up, the compressor motor 1 and the compressor 2 acquire momentum that insures against stalling.

In addition to the roles that the bypass 14 and the valve 13 play in permitting the use of shorter cooling cycles and in keeping the temperature within the refrigerator or freezer more constant they also function as important elements of a defrosting system. A defrosting system employing the valve 13 and the by-pass 14 may be set into operation by a timer or other device after a predetermined interval, and thrown out of operation by a thermostatic device when the temperature of a heat sensitive element has reached a predetermined level. For simplicity of illustration and also because a timer control is reliable and relatively inexpensive, a simple timer control is described herein and diagrammed in the accompanying drawings.

As shown in the diagram of Fig. III a timer motor 20 is wired in parallel with the compressor motor 1 so that the timer motor runs whenever the compressor motor runs. Alternatively, the timer motor 20 can be connected to a source of current independently of the compressor motor 1, as indicated by the diagram of Fig. IV, so that the timer motor will run continuously. With either arrangement, a timer 21 is constructed and adjusted to close a switch 22 after the timer motor 20 has been running for a suitable period such as eight hours during which ice will have been accumulating upon the evaporator. The rate at which ice accumulates is dependent upon the relatively humidity of the air in the box. Since the relative humidity usually is higher in warm weather when the compressor motor 1 runs for a greater part of the time, and since defrosting usually is needed more often on warm days, there is some advantage in causing the timer motor 20 to run more of the time on the days when the compressor motor 1 runs more of the time.

When the switch 22 is closed by the timer 21, the solenoid 12 is energized to cause the valve 13 to open the by-pass 14 from the hot gas conduit 5 into the evaporator 4. The condition of the apparatus when the bypass 14 is opened in response to the action of the timer 21 is quite different from the condition hereinbefore described in which the by-pass 14 was opened as a re-.

sult of action of the' thermostat 8. When the by-pass 14 is opened by the timer the compressor 2 continues to run and the fluid that travels to the evaporator 4 through the by-pass 14 is not partially cooled fluid that backs out of the condenser, but is newly compressed and heated gas that continues to be pumped by the compressor through the by-pass and into the evaporator.

The timer 21 is designed to keep the switch 22 closed for a predetermined short interval, approximately long enough to melt the ice that has accumulated, but not long enough to raise the temperature of the evaporator substantially above 32 F.

While the refrigerating system so far described may be used with variously arranged refrigerator boxes, it is particularly adapted for use in the type of refrigerator box illustrated in Figs. 1 and II of this application, and the advantages of the refrigerator box illustrated in Figs. I and II are particularly enhanced when the above described refrigeration system is incorporated therewith. The refrigerator box generally indicated by the numeral 30 consists of an inner shell 31 having a floor 32, side walls 33 and 34, a ceiling 35 and a back wall 36. Surrounding the inner shell 31 is an outer covering 37, and interposed between the inner shell 31 and the outer covering 37 is a thick layer of thermoinsulation material 38.

Extending over the entire back wall 36 of the inner shell except along the ceiling 35 is a partition plate 39 which is spaced somewhat from the back wall 36.

Adjacent the floor 32 of the inner shell 31 is an inlet port 40 through the partition plate 39, and mounted behind the inlet port is an exhaust fan 41 which draws air through the port 40 and discharges it into the space between the partition plate 39 and the rear wall 36 of the inner shell. Air which is discharged into this space moves upwardly among the coils of the evaporator 4 and passes through a slot 42 which extends along the upper edge of the partition plate 39 just below the ceiling 35 of the inner shell 31, whereby the air throughout the interior of the inner shell 31 is recirculated and thus thermally homogenized.

Interposed in the current of air that is drawn through the'inlet port 40 is the bulb 43 of a thermostatic control device 8. A tube 45, preferably passing through a protective conduit that is buried in the thermoinsulation material 38, leads from the bulb 43 to the thermostatic control device 8, the tube thus being protected against the influence of temperature changes to which it might otherwise be subjected at points between the bulb 43 and the thermostatic control device 8.

When the temperature of the air being withdrawn through the port 40 drops to a low predetermined point and the fluid in the bulb 43 contracts accordingly, the thermostatic control device 8 closes a circuit through the connection 9 to start the compressor motor 1. Conversely when the temperature of the air being withdrawn through the port 40 rises to a higher predetermined point the thermostatic control device 8 opens the circuit through the connection 9 to stop the compressor motor.

Thus, whenever the temperature of the air being withdrawn through the port 40 drops to a low predetermined point the compressor stops until the ingress of heat through the walls and thermoinsulating material of the box and/or the opening of the door to the box causes the temperature to rise to the higher predetermined point, whereupon the condenser restarts. The exhaust fan is turned by a small separate motor (not shown) which may run continuously whenever the refrigerator master switch is closed and the refrigerator system is plugged in, or the fan motor may be wired in parallel or in series with the compressor motor to run only when the compressor motor runs.

By so devising the mechanism that a single valve and by-pass perform multiple functions this invention provides a simple, compact, economical refrigerating system which is capable of maintaining refrigerating temperatures with minimum variations and of operating with high efficiency in changing environments and which also is capable of highly efficient defrosting operations whether controlled manually or by time or temperature. It is to be understood that the system described herein and diagrammed in the accompanying drawings is exemplary only and that the invention includes such modifications as fall within the spirit and scope of the disclosed invention.

I claim:

1. In a refrigerating system, in combination, a compressor, a compressor motor, a condenser, an evaporator, a hot gas conduit leading from said compressor to said condenser, a restricted passage leading from said condenser to said evaporator, a return conduit leading from said evaporator to said compressor, a by-pass to conduct hot gas prior to transformation to a liquid phase from said hot gas conduit to said evaporator, electrically operated means for opening and closing said by-pass, cur

rent directing means for either directing current to energize said compressor motor and to cause said electrically operated means to close said by-pass or alternatively directing current to deenergize said compressor motor and cause said electrically operated means to open said by-pass to conduct such hot gas, a thermostatic control operating at a predetermined low temperature to cause said current directing means to direct current to deenergize said compressor motor and cause said electrically operated means to open said by-pass (whereby said compressor stops and the head pressure against which said compressor works when started is reduced by the release of such hot gas), said thermostatic control operating at a predetermined higher temperature to cause said current directing means to direct current to energize said compressor motor and cause said electrically operated means to close saidby-pass (whereby said compressor starts against reduced head pressure and said valve recloses said by-pass and thus causes such head pressure again to build up), an auxiliary circuit to activate said electrically operated means to open said by-pass independently of the state of energization of said compressor motor, and means'for making and breaking said auxiliary circuit whereby said by-pass is opened for intervals to conductheated gas into heating relationship with said evaporator.

2. In a refrigerating system, in combination, a compressor, a compressor motor, a condenser, an evaporator, ah'ot gas conduit leading from said compressor to said condenser, a restricted passage leading from said condenser to said evaporator, a return conduit leading from said evaporator to said compressor, a by-pass to conduct hot gas prior to transformation to a liquid phase from said hot gas conduit to said evaporator, electrically op-' erated means for opening and closing said by-pass, current directing means for either directing current to energize said compressor motor and to cause said electrically operated means to close said by-pass or alternatively directing current to deenergize said compressor motor and cause said electrically operated means to open said bypass to conduct such hot gas, a thermostatic control operating at a predetermined low temperature to cause said current directing means to direct current to deenergize said compressor motor and cause said electrically operated means to open said by-pass (whereby said compressor stops and the head pressure against which said compressor works when started is reduced by the release of such hot gas), said thermostatic control operating at a predetermined higher temperature to cause said current directing means to direct current to energize said compressor motor and cause said electrically operated means to close said by-pass (whereby said compressor starts and said valve reeloses said by-pass and thus causes said head pressure again to build up), an auxiliary circuit to activate said electrically operated means to open said by-pass independently of the state of energization of said compressor motor, and means for making and breaking said auxiliary circuit whereby said by-pass is opened for intervals to conduit heated fluid into heating relationship with said evaporator, said means for making and breaking said auxiliary circuit including a timer constructed to close said auxiliary circuit intermittently.

3. In a" refrigerating system, in combination; a compressor; a condenser; an evaporator; said compressor being connected to said condenser by a hot gas conduit; said condenser being connected to said evaporator through a restrictor; said evaporator being connected to said compressor by a return conduit; said hot gas conduit being connected to said evaporator through a normally closed bypass valve; control means for said bypass valve adapted to open said valve when said compressor is not running; defrost control means for said bypass valve adapted to open said bypass valve when said compressor is running in response to a defrost signal.

4. In a refrigerating system, in combination; a compressor; a condenser; an evaporator; said compressor being connected to said condenser by a hot gas conduit; said condenser being connected to said evaporator through a restrictor; said evaporator being connected to said compressor by a return conduit; said hot gas conduit being connected to said evaporator through a normally closed bypass valve; control means for said bypass valve adapted to open said valve when said compressor is not running; defrost control means for said bypass valve adapted to open'said bypass valve when said. compressor is running in response to a defrost signal; partition means cooperating with a rear wall of a storage chamber to form a space in which said evaporator is disposed; an air intake port formed at the bottom of said partition; thermostatic control means .for said compressor having a temperature sensitive element located in said air intake port.

'5. In a refrigerator having a chamber, a portion of said chamber being adapted to contain materials to be cooled; said chamber having a floor, side walls, a back wall and a ceiling, such refrigerator also having mechanism for acting upon a refrigerant and including a compressor, a condenser, an evaporator, a hot gas conduit from the compressor to the condenser, a restricted passage from the condenser to the evaporator and a return conduit from the evaporator to the compressor and a motor to operate the compressor, whereby refrigerant in a gaseous phase is compressed and thereby heated by the compressor and is forced in heated and compressed condition' through the hot gas conduit into the condenser where it is cooled by radiation while compressed and thereby transformed into a liquid phase and is forced through the restricted passage into the evaporator where it vaporizes and absorbs heat thereby cooling air surrounding the evaporator, the combination in such refrigerator of a partition located adjacent said back wall and extending between said side walls and upwardly from said floor into juxtaposition to said ceiling, there being a space between said partition and said back wall, an evaporator located in such space, port means located adjacent said floor, at least one opening located adjacent said ceiling and leading from the space in which said evaporator is located into the portion of said chamber that is adapted to contain materials to be cooled, air propelling means to withdraw air from such portion of said chamber through said port means and cause the air so withdrawn to pass upwardly through the space in which said evaporator is located and to flow through said opening adjacent said ceiling, and a thermostat having a temperature sensitive element located in the stream of air being withdrawn through said port means and exposed to a major portion of such stream of air, said thermostat being so electrically connected to said motor as to energize said motor when the temperature of the stream of air in which said temperature sensitive element is located reaches a predetermined high point and to stop said motor when the stream of air in which said temperature sensitive element is located falls to a predetermined lower point; a normally closed' fluid shunt around said restricted passage, means operative upon the stopping of said motor to open said fluid shunt and quickly relieve back pressure against said compressor and means operative upon energization of said motor to close said fluid shunt, and means for periodically holding said shunt open and keeping said motor energized for predetermined intervals notwithstanding temperature variations to which said temperature sensitive element is subjected.

References Cited in the file of this patent UNITED STATES PATENTS 2,350,249 Osborn May 30, 1944 2,430,938 Leeson Nov. 18, 1947 2,635,433 Schordine Apr. 21, 1953 2,635,439 Philipp Apr. 21, 1953 2,737,030 Philipp Mar. 6, 1956 2,745,255 Philipp May 15, 1956 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N00 2 962 87l December 6 1960 Frank Po Crotser It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column L line 61 for relatively reqd relative column 5 line 53, for "closes" read opens ---5 line 54 for start read stop line 57 for "opens" read closes line 58 for "'stop" read start line 65 for oon-= denser read compressor -q,

Signed and sealed this 5th day of June 1962,

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents 

